a) Field of the Invention
The present invention relates to improvement of a motor allowing rotation while urging an end of its center shaft of a rotor in the axial direction.
b) Description of the Related Art
FIG. 4 shows conventional structure of a motor allowing rotation while urging an end of its center shaft of a rotor in the axial direction.
In a motor of FIG. 4, a pair of inside stator cores 51a and outside stator cores 51b are arranged in a shaft direction.
A coil bobbin with a wound winding is provided between the inside stator cores 51a and the outside stator cores 51b. 
Rotor 52 is positioned rotatably within said inside stator cores 51a and outside stator cores 51b. 
Each outside stator cores 51b serves as an outer enclosure case covering the motor from outside in an axial direction and in a radial direction which becomes the outside of the winding.
And an end face in an outside part of each winding of both outside stator cores 51b is fixed by welding (as shown in a weld, T1).
Cap member 54 is fixed to one edge surface of one outside stator core 51b in a shaft direction (corresponding to the end surface of an outer packing retaining shield) by welding (as shown in weld, T2).
Bearing 60 is fitted in cap member 54 and bearing 60 supports one end of center shaft 53 of rotor 52.
Furthermore, at the outside of the cap member 54, urging member 65 is attached having spring 65a which urges bearing 60 toward the direction of a bearing 63 (a bearing held by frame 55 is shown).
In addition, frame 55, which is substantially U-shaped, is fixed to one of the end faces of the side of the other outside stator core 51a (corresponding to an end face of the outer enclosure case) by welding (as shown in a weld, T3).
As described above, one end of center shaft 53 of rotor 52 is supported by bearing 60 which fits in inside of cap member 54.
And another end goes through stator 51 and protrudes to a greater degree than another end side.
That is, center shaft 53 of rotor 52 is inserted in hole 61a which is formed on plane portion 61 of the side fixed to stator 51 of frame 55 and end part of center shaft 53 is supported by bearing 63 that is fitted in plane portion 62.
In addition, the circumference of center shaft 53 is composed of reed screw portion 57.
As described above, the motor is configured to rotate while loading (preloading) the end of center shaft 53 of rotor 52 to bearing 63 arranged in frame 55 by urging bearing 60 toward the direction of bearing 63.
The reason is because rotor 52, caused to rotate mainly on center shaft 53, rotates in a stable state against stator 51 at a predetermined position.
Both control of the dimension (measurement) of the full length in an axial direction of center shaft 53 and control of the spring power of spring 65a of urging member 65 need to be strictly done because rotor 52 cannot rotate smoothly at the predetermined position. Thus these controls are important in such a motor.
In addition, control of the dimension (measurement) of the full length of center shaft 53 in an axial direction is done by controlling the dimension (measurement) between the deepest portions of each hole of both bearings 60, 63 (as shown in FIG. 4, L1).
Control of the spring power of spring 65a of urging member 65 is done by controlling the dimension (measurement) from mounting surface to mount cap member 54 to hold bearing 60 in one outside stator core 51b to the right-side end in FIG. 4 (as shown in L6) and a control of distance (L7) is done from a point of action of spring 61a to a position to abut with bearing 60 on center shaft 53.
Control of dimensions (measurements) in an axial direction of both outside stator core 51b which are faced and arranged in rotor 52 (as shown in L4, L5) and control of dimensions (measurements) of the full length of the whole stator (L4+L5) in an axial direction are important in order to precisely make above described L1.
As described above, in order to control the distance from a point of action of spring 65a of urging member 65 to an abutting position with bearing 60 on center shaft 53, control of a dimension (measurement) in an axial direction from welding surface with one outside stator core 51b of cap member 54 to urging member 61 (as shown in L6) is important, too.
However, the above described motor has the constitution that both outside stator cores 51b are laminated and welded, as well as both sides in the axial direction welded frame 55 and cap member 54.
Therefore it is difficult to control the dimension (measurement) of the full length of stator 51 side corresponding to the full length of center shaft 53 of rotor 52.
In other words, as described above, both outside stator core 51b (L4+L5) and the dimensions (measurements) from the welding surface that frame 55 and stator core 51b contact with the surface of the inside of plane portion 62 (stator 51 side) (L3), therefore, it is necessary to carefully control the dimensions (measurements) of each part in forming a member of several parts.
Thus, when assembling, there is the problem that great confusion results in producing the required overall dimension (measurement) and clearance of each part is difficult.
In addition, when welding these parts, it is necessary to indicate that thickness of a welded location varies by pressure force in a calculation of the overall dimension, so that the work is extremely difficult.
Cap member 54 for holding urging member 65 has the structure that is fixed to one outside stator core 51b by welding as described above so that the above described problem occurs between stator core 51b and cap member 54.
Therefore, confusion may exist concerning the distance L7 from a welding surface between outside stator core 51b and cap member 54 to an out side surface of urging member 65.
As a result, the motor has the overall problem that confusion results in the dimension (measurement) of distance(L6) from a point of action of spring 65a to an abutting position with bearing 60 on center shaft 53.
In other words, even if it is assumed that all dimension (measurement) control of above described L1 . . . L7 (L2=dimensions(measurements) from a deepest portion of a hole of bearing 63 to a mounting portion to mount bearing 63 in frame 55) can be strictly controlled, the above described motor still includes the problem that confusion occurs in determining a dimension (measurement).
It is a primary object of the invention to provide a motor which can easily and precisely control the dimensions (measurements) of a stator part which faces and is arranged with a rotor and also controls the urging power of a spring for urging the rotor in a direction of the frame.
In accordance with the invention, a rotor comprises a stator, a rotor being arranged in and facing said stator, an urging member which urges a center rotation shaft of the rotor in an axial direction, and a bearing which rotatably holds the rotor at a predetermined position while receiving an urging force by the urging member. The stator is provided with a resin coil bobbin made by insert molding and integratedly assembled with a metal stator core. The stator core is arranged in and faces the rotor and forms a magnetic circuit therewith. The coil bobbin is arranged at the end side of the rotor. A holding portion is integratedly formed, the holding portion holds the urging member so as to urge the rotor to the bearing side. A curling base is fitted in. The curling base is formed such that a flat plate-shaped metal plate is rounded from outside of a winding wound by the electric coil bobbin in the circumference direction of the stator.